Ostomy patients with flush or recessed stomas have found that if external pressure is applied in the peristomal region, sufficient protrusion of the stoma may occur to aid in the discharge of effluent directly into the collection pouch, thereby prolonging the effectiveness of the adhesive seal between the faceplate and the peristomal skin surfaces. Skin irritation and patient discomfort may also be greatly reduced. In some cases, such pressure has been applied by means of a sealing ring formed of karaya or other soft, pliable, skin barrier material; however, the deformability and cold-flowability of such a ring limits its effectiveness, or at least the duration of its effectiveness, in achieving adequate stomal protrusion. Some manufacturers of ostomy appliances have therefore introduced relatively rigid convex annular inserts for use with the coupling rings of adhesive faceplates having skin barrier wafers attached thereto. In theory, such an insert is intended to deform the skin barrier wafer to increase peristomal pressure when the appliance is worn but, in practice, the insert usually lacks sufficient convexity to produce a significant change in the contour of the wafer. Inserts with greater convexity have been unavailable, presumably because of the excessive forces that would seem to be necessary, and the damage a faceplate coupling ring might sustain, in fitting such an insert into place. A conventional convex insert has the further disadvantage of requiring attachment from the outer or distal side of a faceplate. Consequently, in the case of a two-piece appliance with disconnectable coupling rings, there is the risk, indicated above, that the faceplate coupling ring might be deformed or damaged when the insert is forced into place; in the case of a one-piece appliance, where a pouch and faceplate are permanently connected, there is the inconvenience that the insert must be fed upwardly through the drainage opening of the pouch so that it may be snapped into position from within the pouch.